Fabrication And Sensing Properties Of Metal-Organic Frameworks Photonic Films

Metal-organic frameworks represent a class of hybrid materials with promising properties for organic vapor sensor due to their large internal surface area, permanent thermal stability, highly chemical tailorability and tremendous structural diversity. This article focused on building label-free and naked-eye MOFs-based optical film sensors. MOFs single layer photonic films, MOFs/TiO₂ alternative multilayer photonic films and MOFs photonic films sensing array were fabricated based on MOFs and TiO₂ nanoparticles. Moreover, the sensing properties of the photonic films deposited on a silicon wafer are evaluated. The major work and conclusions of the article are summarized as follows.?1? Fabrication and sensing properties of MOFs single layer photonic films. NH₂-MIL-88 B single layer photonic films were fabricated by the simple spin-coating technique. A systematic study on the effect of NH₂-MIL-88 B concentration, rotation speed and rotation cycles for the thickness and optical quality of coated films are presented. Moreover, the resulting NH₂-MIL-88 B photonic film can selectively respond to various organic vapors and directly translate into a color-change for naked-eye sensing, which benefits from large swelling-shrinkage of NH₂-MIL-88 B in different organic vapors.?2? Fabrication and sensing properties of MOFs/TiO₂ alternative multilayer photonic films. MOFs/TiO₂ alternative multilayer photonic films with vivid structural colors were fabricated by alternate spin-coating of NH₂-MIL-88 B solution and titania sol. The optical properties of the alternative multilayer photonic films were tailored by changing the number of bilayers, physical thickness, or high temperature treatment. Moreover, a selective quantitative measurement of ethanol concentration was successfully performed when the alternative multilayer photonic films was exposed to the vapors of mixture of ethanol and water. In addition, the alternative multilayer photonic films have highly thermal and ultrasonic stability, and can maintain high performance for long-terms storage, which benefits for the practical applications.?3? Fabrication and sensing properties of MOFs photonic films sensing array. A novel sensing array was developed by using different kinds of MOFs photonic films as sensing elements in order to improve the selectivity of photonic films. We evaluate each sensing element by observing UV-Vis reflection spectrum. The sensing results were analyzed by combining these shifts of reflection peaks. The special shift corresponding to each sensing element of sensing array form fingerprint spectrum to identify organic vapors. The sensing array can distinguish alcohols, alkanes and water by Principle Components Analysis. The sensing array also can easily classify the target molecule by Hierarchical Clustering Analysis. Me OH, Et OH, and i-Pr OH belong to one kind owing to the intrinsic relation of chemical structure, water and heptane can be divided into other two kinds.